This invention relates to a gradation fluorescent display device, and more particularly to a fluorescent display device adapted to carry out gradation display.
Now, a conventional color fluorescent display device of the gradation display type will be described with reference to FIGS. 10(a) and 10(b), which are a sectional view of the fluorescent display device and a plan view partly in section taken along line Xxe2x80x94X of FIG. 10(a), respectively.
In FIGS. 10(a) and 10(b), reference numeral 91 designates a glass substrate, 92 is a front glass member, 93 to 96 each are a side glass member, 97l to 97n each are an anode electrode, 98l to 98n each are a phosphor film deposited on each of the anode electrodes, 99 designates grids, and 100 designates filamentary cathodes.
The anode electrodes 97l to 97n and phosphor films 98l to 98n cooperate with each other to constitute n (n: positive integer) display segments, which are arranged in a pattern shown in FIG. 10(b).
The phosphor films 98l to 98n each have a luminous hue stepwise varied for every phosphor film, resulting in carrying out gradation display. The phosphor films each are made of two or more phosphors mixed together. The phosphors are mixed in a different mixing ratio for every phosphor film, so that the phosphor films may be stepwise varied in luminous hue. This is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 165557/1980.
In the conventional fluorescent display device of the gradation display type, as described above, it is required to vary a mixing ratio of phosphors for every display segment or every phosphor film of the display segment. Thus, when n such display segments are arranged, it is required to prepare phosphors of n types different in mixing ratio, to thereby prepare phosphor pastes of n types. For example, when 10 such display segments are arranged, phosphor pastes of 10 types are required.
Also, in order to permit the conventional fluorescent display device of the gradation display type to carry out desired gradation display, phosphors for the phosphor film of each of the display segments must be accurately mixed at a predetermined mixing ratio. A luminous hue of the phosphor film is delicately varied depending on mixing of the phosphors, resulting in control of the mixing ratio and operation of mixing the phosphors being highly troublesome.
N types of phosphor pastes are used for formation of the phosphor films, so that operation of coating or applying the phosphor pastes must be repeated n times. An increase in number of times of application of the phosphor pastes causes a phosphor paste applied at earlier stages to be pressed or rubbed by masks for application used at later stages or polluted by phosphor pastes applied at later stages, to thereby often cause a deterioration in luminous efficiency of the phosphor films or color shading in luminous hue. Also, it may possibly lead to peeling-off of the phosphor pastes applied at earlier states. Further, in order to execute application of the phosphor pastes at later states in the application step, drying of the phosphor pastes applied at earlier stages is required. Thus, an increase in number of types of phosphor pastes causes a long period of time to be required in the application step, leading to a deterioration in manufacturing efficiency.
Further, in the prior art, the phosphor films each are formed of phosphors of two or more types different in life, so that a luminous hue of the phosphor film is often varied with time due to a difference in life between the phosphors.
Moreover, the conventional fluorescent display device of the gradation display type requires to develop phosphors of new hues in conformity to gradations desired. Unfortunately, such development is time-consuming and costly, resulting in failing to satisfactorily meet requirements on gradations demanded by consumers.
The present invention has been made in view of the foregoing disadvantages of the prior art.
Accordingly, it is an object of the present invention to provide a fluorescent display device which is capable of carrying out gradation display without mixing phosphors with each other.
In accordance with the present invention, a fluorescent display device is provided. The fluorescent display device includes a plurality of display segments each including an anode electrode and a phosphor film deposited on the anode electrode. The phosphor film is constituted by phosphor film elements different in luminous hue which are arranged in juxtaposition to each other. The phosphor film elements different in luminous hue of each of the phosphor films have an area ratio therebetween varied depending on the display segment.
Also, in accordance with the present invention, a fluorescent display device is provided. The fluorescent display device includes a plurality of display segments each including an anode electrode and a phosphor film deposited on the anode electrode. The phosphor film is constituted by phosphor film elements different in luminous chroma or luminous lightness which are arranged in juxtaposition to each other. The phosphor film elements different in luminous chroma or luminous lightness of each of the phosphor films have an area ratio therebetween varied depending on the display segment.
Further, in accordance with the present invention, a fluorescent display device is provided. The fluorescent display device includes a plurality of display segments each including an anode electrode and a phosphor film deposited on the anode electrode. The phosphor film of each of the display segments has an area varied in order depending on the display segment.
In a preferred embodiment of the present invention, the phosphor film of a part of the display segments is constituted by one kind of phosphor film element.
In a preferred embodiment of the present invention, the display segments constitute a display segment group. The area ratio between the phosphor film elements is varied depending on the display segment group.
In a preferred embodiment of the present invention, an area of each of said display segments is varied depending on the display segment.